1. Field of the Invention
The present invention relates to a plasma display panel (hereinafter "PDP") used in a plasma display apparatus, and particularly to a structure of a barrier rib for partitioning adjacent unit cells.
2. Description of the Invention
The PDP utilizes an emission caused by an electric discharge between the crossovers of matrix electrodes in a rare gas mixture. A basic structure of the PDP is constructed by a plurality of line electrodes and row electrodes spaced therefrom which are formed on two glass plates respectively, and a discharge space (about 0.1 mm spaced) which is filled with a rare gas mixture containing Neon (Ne) mainly at hundreds Torr. The PDP is generally classified into the DC type (or direct discharge type) in which the electrodes are exposed in the discharge space and the AC type (or direct discharge type) in which the electrodes are covered with a dielectric layer. The AC type PDP is driven by a voltage application method such as a refresh method, a matrix address method, self-shift method and so on.
FIG. 1, for example, shows an AC type PDP with a matrix address method which comprises a face plate 1 and a rear plate 2 facing and parallel to each other, and a discharge gas space 4 defined by these plates and insulating barrier ribs 3. The barrier rib partitions pixel cells to prevent the adjacent cells from leaking ultraviolet rays produced by the electrical discharge. In addition, the barrier rib is generally formed of a light-absorbing material to prevent the reflection of incident lights entering from the outside and improve the contrast of an image displayed on the PDP.
A plurality of address electrodes W are formed parallel to each other on the rear plate 2. A dielectric layer 23 is formed on and over the address electrodes W. A plurality of pairs of sustaining electrodes S are formed parallel to each other on the dielectric layer 23 so as to cross the address electrodes W. Another dielectric layer 23 is formed on and over the sustaining electrodes S. A MgO layer 24 is formed on this dielectric layer 23. Barrier ribs 3 are formed on the MgO layer 24 by means of a printing method so as to rise above the surface of layer 24.
A face plate 1 is put on and over the tops of the barrier ribs. Fluorescent layers 11 are formed on the internal surface of the face plate so as to correspond to unit cells respectively. The face plate 1 and the rear plate 2 are aligned with each other and then assembled, after which a discharge gas space 4 is defined into which a rare gas mixture is injected. In this way, a transparent type PDP is manufactured.
This PDP is operated as follows: When a predetermined voltage is applied across each pair of the address electrodes W and the sustaining electrodes S embedded in the dielectric layer, a discharging region appears above the rear plate 2 at the crossover point of each pair of electrodes. Ultraviolet rays emitted from the discharging region stimulate the fluorescent layer 11 to emit light, and an emission region is produced in the discharge gas space 4. This discharged emission is maintained by a sustaining voltage applied between the sustaining electrodes, but canceled by an erase pulse applied between the address electrodes W.
In addition, a reflecting type PDP has been proposed in which a fluorescent layer is additionally formed in the internal surface of the barrier rib or the rear plate, so that the area of emission is expanded, to thereby provide an improvement of emission efficiency in comparison with forming the fluorescent layer in only the inner surface of the face plate, as in the above transparent type PDP. Even with such an arrangement, all light emitted from the discharging region or the fluorescent layer does not radiate through the display surface. A part of the light is absorbed by the barrier rib and another part is leaked from the rear plate. Accordingly, there is a strong demand in the art for improving the emission efficiency of PDPS.